Concentrations Of Medium-chain Fatty Acids Research Articles

Lactation in lean and obese rats: Effect of cafeteria feeding and of dietary obesity on milk composition

Changes in milk composition associated with maternal dietary obesity and cafeteria feeding were investigated. Protein, lactose and fat contents, and the fat composition, were determined for lean and obese rats given a cafeteria diet at different stages of reproduction. Feeding the cafeteria diet during lactation resulted in an increase in long-chain fatty acids and a fall in the characteristic medium-chain fatty acids. This effect was modified by obesity and the diet during pregnancy. Feeding the cafeteria diet in lactation reduced the milk protein and increased the fat. The milk of obese rats contained more energy, with more fat but less protein than that of lean rats. Increases in fat and long-chain fatty acid content, and decreases in protein and medium-chain fatty acid content of the milk were correlated with increased maternal intake of energy, total fat and long-chain fatty acids. Thus, the greatest influence on milk composition is exerted by the maternal diet during lactation. However, these effects are modified by pre-existing maternal obesity and the diet during pregnancy.

Apparent decreased oxidation and turnover of leucine during infusion of medium-chain triglycerides.

A potential effector of the protein-sparing adaptation to fasting could be the increased availability of endogenous long-chain fatty acids. Were this hypothesis correct, infusion of medium-chain triglycerides to increase the plasma concentration of medium-chain fatty acids might also result in protein sparing. However, in most in vitro studies in rat muscle, octanoate increases the oxidation of the essential amino acid leucine. Therefore leucine metabolism was assessed with infusions of [3H]leucine and a-[14C]ketoisocaproate ([14C]KIC) before and during an infusion of trioctanoin in conscious dogs. Plasma octanoate increased from less than 30 to 528 microM over the 3 h of infusion. Plasma leucine and KIC concentrations decreased by 65-70% (P less than 0.01) over the first 2 h of infusion. Leucine oxidation, estimated from the expired 14CO2 and the plasma [14C]KIC specific activity, as well as from an open two-pool model, decreased. By use of these isotope models, the rates of leucine coming from and going to protein decreased (P less than 0.05 to P less than 0.01). Interconversion of leucine and KIC estimated from the open two-pool model decreased by 80% (P less than 0.01). These changes were accompanied by a 36% decrease in the plasma concentration of total plasma amino acids. Within the confines of the isotope models employed, these data are consistent with the hypothesis that increased fatty acid oxidation decreases protein turnover and may spare essential amino acids.

Gastric lipolysis of milk lipids in suckling rats

Fatty acid composition of the major lipid classes in stomach contents of suckling rats at 1, 5, 10, 17 and 20 days of lactation was compared to that of milk lipids. In milk, 98% of fatty acids were in triacylglycerols at all lactation times. Medium-chain fatty acid concentrations increased from 8% in colostrum to 26% at day 5. Fatty acid composition of stomach acylglycerols at all lactation times was different from that of milk triacylglycerols, containing less medium-chain fatty acids, 8:0 and 10:0. This preferential hydrolysis was also shown by higher concentrations of medium-chain fatty acids in the free fatty acid fraction. The lipolysis of medium-chain fatty acids from triacylglycerols resulted in the appearance of di- and monoacylglycerols with 50–100% higher amounts of 14:0 and 16:0. The similar fatty acid composition of products suggests that considerable lipolysis occurred in stomachs of suckling rats even at 1 day of age. Although there was a 10-fold increase in milk consumption, the extent of lipolysis was similar throughout the suckling period because of a parallel rise in lingual lipase levels.

Comparison of the lipid composition of breast milk from mothers of term and preterm infants

Milk was collected from mothers of 18 very premature (26 to 30 wk gestation age), 28 premature (31 to 36 wk), and six term (37 + wk) infants on day 2 to 3 (colostrum), and at 1, 3, 6, and 12 wk postpartum. Fat content for 154 milk samples was 2.80 g/dl gravimetrically and 2.66 g/dl by quantitative thin-layer chromatography. Fat content increased during lactation, whereas phospholipids and cholesterol declined. Concentrations of medium-chain fatty acids increased from colostrum to mature milk and were highest in preterm milk. Compensatory decreases were observed in very premature and premature oleic acid. Long-chain polyunsaturated fatty acids were highest in colostrum and reduced in mature milk. Long-chain polyunsaturated fatty acids were also higher in very premature and premature milk than in term milk. These elevated levels of readily absorbed medium-chain fatty acids and long-chain polyunsaturated fatty acids in preterm milk may be of special benefit for the needs of premature infants.

Effect of Dietary Short- and Medium-Chain Fatty Acids on Feed Intake by Chicks

Seven short- and medium-chain fatty acids and three industrial grade mixtures of medium-chain fatty acids were evaluated for their potential as feed additives for the regulation of feed intake as chicks. Voluntary feed intake of 7- to 21-day-old broiler chicks decreased when substituting propionic, caprylic, capric, or lauric acids for corn oil at 30 g/kg, but not with acetic, butyric, or caproic acids.Negative linear responses to caprylic and lauric acids were found over the range of dietary content of 0 to 100 g/kg, with regression coefficients (b) = −5.6 and −5.9 g feed intake/g fatty acids/kg feed (r2 = .84 and .81), respectively, for 1- to 29-day-old chicks. Feed intake response to industrial grade lauric acid and coconut fatty acids, when included at 7% level, was similar to that predicted from their content of medium-chain fatty acids of 980 and 590 g/kg. Thirty g/kg pelargonic acid gave a 50% reduction in feed intake and weight gain in 1- to 29-day-old chicks. A higher mortality was noted in chicks receiving industrial grade fatty acids than in other chicks.